Discharge section structure for centrifugal compressor

Abstract

Provided is a discharge section structure for a centrifugal compressor provided with a scroll flow passage and a discharge flow passage connected to the scroll flow passage. The discharge section structure includes a tongue section provided in a branching section between the scroll flow passage and the discharge flow passage; a first flow passage section having a center of curvature on an origin side of the scroll flow passage; and a second flow passage section communicating with the first flow passage section and having a center of curvature on an outer side of the scroll flow passage. The first flow passage section includes at least a part of the scroll flow passage, and the second flow passage section includes at least a part of the discharge flow passage. The tongue section faces the second flow passage section and is located in the middle of the second flow passage section.

The invention claimed is: 
     
       1. A discharge section structure for a centrifugal compressor provided with a scroll flow passage and a discharge flow passage connected to a discharge side of the scroll flow passage, the discharge section structure comprising:
 a tongue section provided in a branching section between the scroll flow passage and the discharge flow passage; 
 a first flow passage section having a first center of curvature on an origin side of the scroll flow passage, the first flow passage section including a first inner wall section and a first outer wall section each with respect to the first center of curvature; and 
 a second flow passage section communicating with the discharge side of the first flow passage section and having a second center of curvature outside of the scroll flow passage, the second flow passage section including a second inner wall section and a second outer wall section each with respect to the second center of curvature, 
 wherein the first flow passage section includes at least a part of the scroll flow passage, 
 the second flow passage section includes at least a part of the discharge flow passage, 
 the tongue section faces the second flow passage section and is located upstream of the part of the discharge flow passage, and the second flow passage section includes a convex shape formed by the second outer wall section and an imaginary surface extending from an upstream end of the second outer wall section to the first inner wall section, 
 wherein the convex shape extends continuously in an upstream direction from a downstream end of the second flow passage section to an end of the imaginary surface at the first inner wall section. 
 
     
     
       2. The discharge section structure for the centrifugal compressor according to  claim 1 , wherein the tongue section is located at a central portion of the second flow passage section or on a downstream side of the central portion. 
     
     
       3. The discharge section structure for the centrifugal compressor according to  claim 1 , wherein, in a cross section orthogonal to a central axis passing through the origin of the scroll flow passage, an angle formed between a wall surface of the tongue section on the scroll flow passage side and a wall surface of the tongue section on the discharge flow passage side is 50° or more. 
     
     
       4. The discharge section structure for the centrifugal compressor according to  claim 2 , wherein, in a cross section orthogonal to a central axis passing through the origin of the scroll flow passage, an angle formed between a wall surface of the tongue section on the scroll flow passage side and a wall surface of the tongue section on the discharge flow passage side is 50° or more. 
     
     
       5. The discharge section structure for the centrifugal compressor according to  claim 1 , wherein the at least the part of the discharge flow passage is included in the convex shape. 
     
     
       6. The discharge section structure for the centrifugal compressor according to  claim 1 , wherein the imaginary surfaces passes through a front end of the tongue section.